Comment by Starman_Jones

This problem already exists in retail. Pricing algorithms are easy to run, and paper tags are difficult to change frequently or in bulk. Every store will honor the posted price, but within that there’s still a range of responses between “make the customer happy” and “the onus is on the customer to prove that the register price is incorrect.” Digital signage really tips the scales against the customers proving that the price is wrong, but I expect that most companies will adopt policies closer to the “make the customer happy” end of the spectrum. It’s not worth fighting about $10, especially if you both know they’re right.